Can you tell us some more where its planted and soil type how old it is .

I do have one as well and its doing really well .

Gg

There seems to be a lot of these trees looking ill or dying in the last couple of years.
Mine died and had to be taken down.
The RHS site is aware of the problem but not yet of the cause.

same happening to two of the trees in the park close to the office branches dying back ,, I give my tree a good rose feed in the spring and a good water in the summer if needed, the winter of 2011 took the top leader out so has become more spread out, maybe its the bad winters of 2011/2012 that have taken its toll on them as with trees they can take a couple of years to die off totally with something that has happens in the past

Gg

That's interesting . . . my dwarf Robinia frisia is fine "on top" but most of the lower branches look dead (and it's not really "dwarf" any more). Hope it survives as it's such an attractive tree (mostly!).